Lithograph plate preparation



Patented May 6, 1941 LITHOGRAPH PLATE PREPARATION William H. Wood,Bedford, Ohio, assignor to The Harris-Seybold-Potter Company, Cleveland,Ohio, a corporation of Delaware N Drawing. Application November 21,1938,Serial No. 241,512

4 Claims. (Cl. 101-4011) In lithography, it is common practice tosuitably treat the surface of the plate such that image and non-imageareas are obtained, the latter being characterized by beingnon-receptive of the ink, and water is suitably applied in the printingprocess to maintain these areas sufficiently ink-repellent. customarily,aluminum in pure state is employed as plate material. In accordance withthe present invention, alloy plate mate rials are employed, and withsurprising distinction in properties as contrasted with the customaryaluminum plates.

To the accomplishment ofv the foregoing and related ends, the invention,then, comprises the features hereinafter fully described, andparticularly pointed out in the claims, the following descriptionsetting forth in detail certain illustrative embodiments of theinvention, these being indicative however, of but a few of the variousways in which the principle of the invention may be employed.

In the preparation of; lithographic plates according to the invention, Iapply aluminum alloyed, as hereinafter detailed. Lithographic platesthus made up. are found to have surprisinig moisture-retentiveness. Theyhold a moisture film three to five times as long as the customaryaluminum plates, and as will be readily more accurately controlled. Indeep etching usual aluminumplates, theattack by an iron chloridesolution is so rapid that a plate may be overetched in less than aminute, and skilled operators have great difficulty in controlling theetching to avoid such over-action. In contrast, the present plates willwithstand the action of a a 50 B. iron chloride etch for a period withintwo minutes without over-etching, and the process is easily controlled.r The 'plates are made in usual or desired thickness, and the metal isan alloy of aluminum and manganese. The proportion o f manganesemayappreciated by workers in the art, this involves a remarkable advantagein lithographic printing. Again, less moisture is required in thedampening during printing. Another peculiar characteristic of theimproved plates is that whereas the ordinary aluminum platescannot beleft unprotected by applications of gum etc. for more than fifteen ortwenty minutes without undergoing changes in the atmosphere such thatthere is a diflerence in sensitivity to ink, the present plates may beleft unprotected by the usual gum coating for extended periods.Peculiarly also, using commonly known fountain solutions such asgum-dichromate-phosphoric acid -or phosphoric-gum solution, the presentplates-may be allowed to dry on the press, and can then be inked upsolid, and

then simply by dampening the plate the ink may be removed by the inkrollers or by other means. This is impossible with customary aluminumplates. Peculiarly also, a finer grain is produced in graining thepresent plates, and there is less tendency to warpage from the grainingthan is the case with the usual aluminum plates. The present inventionis notably advantageous in the making of deep etch lithographic plates,for the reason that the-etching action proceeds more slowly than withordinary aluminum and can be in, general be 1 to 2 per cent, and 1.25per cent is very satisfactory. Provided the manganese content bepresent, the presence or absence of smaller amounts of such elements ascopper, iron,

and silicon is immaterial. Such plates may be v features stated in anyof the following claims,

or the equivalent of such, be employed.

I therefore particularly point out and distinctly claim as my invention:

1. In the preparation of lithographic plates, Y

promoting the moisture-retaining capacity of a plate which ispredominantly of aluminum by including a small amount of manganese inthe plate.

2. In the preparation of lithographic plates,

promoting the moisture-retaining capacity of a graphic plate ofpredominantly aluminum and, containing about 1.25 per cent of manganese.

WILLIAM H. WOOD.

